1. Field
One or more embodiments relate to a piezoelectric ultrasonic motor having a driving force due to friction between a vibrator and a rotator, and a method of manufacturing the piezoelectric ultrasonic motor.
2. Description of the Related Art
A piezoelectric ultrasonic motor is a motor that is rotated by friction between a vibrator and a rotator and is driven by applying an ultrasonic driving voltage at a frequency of 20 kHz or greater, which humans cannot detect. Unlike a high speed and high torque electromagnetic motor, the piezoelectric ultrasonic motor has a low speed and a high torque, and may be driven without any additional deceleration gear. Further, the piezoelectric ultrasonic motor has a self-braking function due to frictional force, and does not generate electronic waves since coils or magnetic bodies are not used. Further, precision control may be conducted by using the piezoelectric ultrasonic motor, and the piezoelectric ultrasonic motor may be easily applied to systems, such as precision machines, due to the compact size of the piezoelectric ultrasonic motor. The piezoelectric ultrasonic motor can be used in fields such as robots, medical equipment, cameras, semiconductor testing equipment, building automation equipment, etc. which use super-precision position control.
A rotator and a vibrator of a general piezoelectric ultrasonic motor are manufactured using a metal cutting process, and include a spring structure in contacting bodies where the flatness of a frictional surface of the vibrator is not uniform, in order to maintain uniform friction by pressing the vibrator against the rotator. However, the spring structure of the rotator formed by a cutting process has a complicated shape and a small thickness, and thus, it is difficult to manufacture the spring structure and to control the flatness of the rotator.
Further, in order to increase the resistance of the rotator to abrasion, a thin anti-abrasion coating layer may be formed on surfaces of the vibrator and the rotator. However, when metal is cut to form the spring structure, a burr is generated, and if the anti-abrasion layer is formed without post-process to remove the burr, it is difficult to form the anti-abrasion layer with a uniform thickness. Thus, the anti-abrasion layer can be partially damaged and the anti-abrasion characteristics of the rotator are deteriorated, thereby increasing driving noise and decreasing the efficiency of the piezoelectric ultrasonic motor.